1. Technical Field
The present invention pertains generally to the field of shells for heat exchangers such as intercoolers, and pertains specifically to a nozzle therefor to reduce pressure drop.
2. Prior Art
In many operations or processes fluids are handled and conditioned under circumstances in which it is desirable to minimize the pressure drop which the fluid experiences. For example, intercoolers having a coil, tube bundle or the like disposed within a shell are frequently used in large compressor operations having multiple stages of compression. The intercooler reduces the temperature of the fluid being compressed so that the inlet temperature of a subsequent stage of compression is substantially less than the temperature at the outlet of a previous stage of compression. The power required to achieve the final pressure is reduced by decreasing the inlet temperature at each compression stage. Particularly in very large systems, the decreased operating costs can quickly pay for the increased costs of installing an intercooler, even though the intercooler can be quite costly.
Just as temperature reduction between stages of compression is highly desirable, pressure loss between stages is highly undesirable. The power required to achieve the final level of compression for the fluid increases as the pressure is reduced at each successive inlet of compression stages. Thus, it is extremely important to minimize the pressure loss in a compressor intercooler to minimize operating costs.
Given unlimited freedom of design, engineers could readily design heat exchangers to perform the necessary temperature reduction while minimizing pressure drop. Unfortunately, in the typical compressor, the size, shape and location for an intercooler is substantially limited. Normally, the locations of the inlet and outlet nozzles and the size of the pipes leading to and from the intercooler are fixed; thus, in designing an intercooler for a compressor, the engineer is faced with severe design limitations.
Experience has shown that in many intercooler designs as much as eighty percent (80%) of the total pressure drop experienced in the intercooler occurs at the inlet and outlet nozzles. About half of the pressure drop experienced at the nozzles, or about forty percent (40%) of the total pressure drop in the intercooler, is experienced at each of the nozzles. The present invention deals with a design for minimizing pressure drop at the outlet nozzle.
The effectiveness of a bellmouth orifice for reducing pressure losses in some applications is well known. These have not been used, however, on shells of intercoolers, aftercoolers, knockout drums or other high pressure devices having curved shells because of various manufacturing drawbacks and design limitations. As mentioned previously, the size and location of the connecting pipe is fixed or severely limited. Attaching the periphery of a bellmouth orifice directly to the cylindrical shell wall or to a curved shell cover or end presents many manufacturing difficulties, and the high pressures attained in the shell make it impractical to provide a flat plate area on the shell or end to which the orifice can be attached. To withstand the pressures the plate would have to be unacceptably thick. The present invention overcomes these and other difficulties and makes the use of a bellmouth orifice for a high pressure shell outlet practical.